android studio 使用gradle打jar包并混淆

昨天準備把寫好的代碼使用gradle打jar包出來，并打算加混淆。打jar包容易，結果在混淆上走了彎路。

首先打jar包的配置很簡單，使用jar的task，具體代碼如下：

task buildJar(type: Jar, dependsOn: ['assembleRelease']) {
    destinationDir = file('build/outputs/jar/')
    appendix = ""
    baseName = ""
    version = SDK_VERSION

    // manifest信息
    def map = ['Version': SDK_VERSION,
               'Gradle': project.gradle.gradleVersion,
               'Vendor': '',
               'Date': new Date().getDateTimeString()
        ]
    manifest.attributes(map)

    from('build/intermediates/classes/release/')
    exclude('**/BuildConfig.class')
    exclude('**/BuildConfig\$*.class')
    exclude('**/R.class')
    exclude('**/R\$*.class')
    include('**/*.class')
}

但是發現上面打出來的jar包中的代碼沒有被混淆，于是加混淆。使用混淆的proguard.gradle.ProGuardTask task時，發現總是報如下錯誤：

java.io.IOException: The output jar [....jar] must be specified after an input jar, or it will be empty.

按照上面的提示， outjars 是寫在 injars 后面啊， it will be empty 是提示哪里有問題？以為是 proguard-rules.pro 文件中的配置有問題，結果把文件清空，還是報上面的錯誤，錯誤原因不得而知了。在這個問題上耗了很長時間，最終還是沒有解決。

突然看到上面的 assembleRelease task想起了平常打APK時，會使用到這個task，打出來的APK會自動混淆。那這個 assembleRelease task就會依賴處理混淆的task，于是查看了輸出日志：

To honour the JVM settings for this build a new JVM will be forked. Please consider using the daemon: https://docs.gradle.org/2.14.1/userguide/gradle_daemon.html.
Observed package id 'system-images;android-22;google_apis;x86' in inconsistent location 'android-sdk-windows-studio\system-images\addon-google_apis-google-22
\x86' (Expected 'android-sdk-windows-studio\system-images\android-22\google_apis\x86')
Observed package id 'system-images;android-22;google_apis;x86' in inconsistent location 'android-sdk-windows-studio\system-images\addon-google_apis-google-22
\x86' (Expected 'android-sdk-windows-studio\system-images\android-22\google_apis\x86')
Incremental java compilation is an incubating feature.                
:sdk:preBuild UP-TO-DATE                                                                                                                                                
:sdk:extractProguardFiles
:sdk:preReleaseBuild
:sdk:checkReleaseManifest
:sdk:preDebugAndroidTestBuild UP-TO-DATE
:sdk:preDebugBuild UP-TO-DATE
:sdk:preDebugUnitTestBuild UP-TO-DATE
:sdk:preReleaseUnitTestBuild UP-TO-DATE
:sdk:prepareComAndroidSupportAnimatedVectorDrawable2510Library UP-TO-DATE      
:sdk:prepareComAndroidSupportAppcompatV72510Library UP-TO-DATE      
:sdk:prepareComAndroidSupportSupportCompat2510Library UP-TO-DATE
:sdk:prepareComAndroidSupportSupportCoreUi2510Library UP-TO-DATE
:sdk:prepareComAndroidSupportSupportCoreUtils2510Library UP-TO-DATE
:sdk:prepareComAndroidSupportSupportFragment2510Library UP-TO-DATE      
:sdk:prepareComAndroidSupportSupportMediaCompat2510Library UP-TO-DATE      
:sdk:prepareComAndroidSupportSupportV42510Library UP-TO-DATE
:sdk:prepareComAndroidSupportSupportVectorDrawable2510Library UP-TO-DATE
:sdk:prepareReleaseDependencies
:sdk:compileReleaseAidl UP-TO-DATE      
:sdk:compileReleaseNdk UP-TO-DATE
:sdk:compileLint UP-TO-DATE
:sdk:copyReleaseLint UP-TO-DATE
:sdk:compileReleaseRenderscript UP-TO-DATE
:sdk:generateReleaseBuildConfig                 
:sdk:generateReleaseResValues UP-TO-DATE
:sdk:generateReleaseResources UP-TO-DATE
:sdk:mergeReleaseResources UP-TO-DATE      
:sdk:processReleaseManifest UP-TO-DATE
:sdk:processReleaseResources UP-TO-DATE      
:sdk:generateReleaseSources
:sdk:incrementalReleaseJavaCompilationSafeguard                 
:sdk:compileReleaseJavaWithJavac                 
:sdk:compileReleaseJavaWithJavac - is not incremental (e.g. outputs have changed, no previous execution, etc.).
注: 某些輸入文件使用或覆蓋了已過時的 API。                                                                                                                               
注: 有關詳細信息, 請使用 -Xlint:deprecation 重新編譯。                                                                                                                   
:sdk:extractReleaseAnnotations                   
:sdk:mergeReleaseShaders UP-TO-DATE      
:sdk:compileReleaseShaders UP-TO-DATE
:sdk:generateReleaseAssets UP-TO-DATE
:sdk:mergeReleaseAssets UP-TO-DATE
:sdk:mergeReleaseProguardFiles UP-TO-DATE
:sdk:packageReleaseRenderscript UP-TO-DATE
:sdk:packageReleaseResources UP-TO-DATE      
:sdk:processReleaseJavaRes UP-TO-DATE
:sdk:transformResourcesWithMergeJavaResForRelease UP-TO-DATE
:sdk:transformClassesAndResourcesWithProguardForRelease                 
ProGuard, version 5.2.1
Reading input...                                                        
Reading program directory [sdk\build\intermediates\classes\release] (filtered)
Reading library jar [sdk\build\intermediates\exploded-aar\com.android.support\support-media-compat\25.1.0\jars\classes.jar] (filtered)

Reading library jar [sdk\build\intermediates\exploded-aar\com.android.support\support-compat\25.1.0\jars\classes.jar] (filtered)
Reading library jar [sdk\build\intermediates\exploded-aar\com.android.support\support-fragment\25.1.0\jars\classes.jar] (filtered)
Reading library jar [sdk\build\intermediates\exploded-aar\com.android.support\support-core-ui\25.1.0\jars\classes.jar] (filtered)
Reading library jar [sdk\build\intermediates\exploded-aar\com.android.support\animated-vector-drawable\25.1.0\jars\classes.jar] (filte
red)
Reading library jar [android-sdk-windows-studio\extras\android\m2repository\com\android\support\support-annotations\25.1.0\support-annotations-25.1.0.jar] (f
iltered)
Reading library jar [sdk\build\intermediates\exploded-aar\com.android.support\support-v4\25.1.0\jars\classes.jar] (filtered)
Reading library jar [sdk\build\intermediates\exploded-aar\com.android.support\support-vector-drawable\25.1.0\jars\classes.jar] (filter
ed)
Reading library jar [sdk\build\intermediates\exploded-aar\com.android.support\appcompat-v7\25.1.0\jars\classes.jar] (filtered)
Reading library jar [sdk\build\intermediates\exploded-aar\com.android.support\support-core-utils\25.1.0\jars\classes.jar] (filtered)
Reading library jar [\android-sdk-windows-studio\platforms\android-25\android.jar]
Reading library jar [\android-sdk-windows-studio\platforms\android-25\optional\org.apache.http.legacy.jar]
Note: duplicate definition of library class [android.net.http.HttpResponseCache]
Note: duplicate definition of library class [android.net.http.SslCertificate$DName]
Note: duplicate definition of library class [android.net.http.SslError]
Note: duplicate definition of library class [android.net.http.SslCertificate]
Note: duplicate definition of library class [org.apache.http.params.CoreConnectionPNames]
Note: duplicate definition of library class [org.apache.http.params.HttpConnectionParams]
Note: duplicate definition of library class [org.apache.http.params.HttpParams]
Note: duplicate definition of library class [org.apache.http.conn.scheme.SocketFactory]
Note: duplicate definition of library class [org.apache.http.conn.scheme.LayeredSocketFactory]
Note: duplicate definition of library class [org.apache.http.conn.scheme.HostNameResolver]
Note: duplicate definition of library class [org.apache.http.conn.ConnectTimeoutException]
Note: there were 11 duplicate class definitions.
      (http://proguard.sourceforge.net/manual/troubleshooting.html#duplicateclass)
Initializing...
Note: you're ignoring all warnings!                                     
Ignoring unused library classes...                                      
  Original number of library classes: 5857
  Final number of library classes:    383
Printing kept classes, fields, and methods...
Shrinking...
Printing usage to [sdk\build\outputs\mapping\release\usage.txt]...
Removing unused program classes and class elements...                   
  Original number of program classes: 52                                
  Final number of program classes:    48
Obfuscating...
Printing mapping to [sdk\build\outputs\mapping\release\mapping.txt]...
Writing output...
Preparing output jar [sdk\build\intermediates\transforms\proguard\release\jars\3\3\main.jar]
  Copying resources from program directory [sdk\build\intermediates\classes\release] (filtered)
Printing classes to [sdk\build\outputs\mapping\release\dump.txt]...
:sdk:transformClassesAndResourcesWithSyncLibJarsForRelease                 
:sdk:mergeReleaseJniLibFolders UP-TO-DATE
:sdk:transformNative_libsWithMergeJniLibsForRelease UP-TO-DATE      
:sdk:transformNative_libsWithSyncJniLibsForRelease UP-TO-DATE
:sdk:bundleRelease                 
:sdk:compileReleaseSources
:sdk:assembleRelease
:sdk:buildJar                 

BUILD SUCCESSFUL.

好家伙，被我發現了。其中從 :sdk:transformClassesAndResourcesWithProguardForRelease 這個task就可以看到，下面一堆日志是關于 ProGuard 混淆工具的，最后可以看到：

Preparing output jar [sdk\build\intermediates\transforms\proguard\release\jars\3\3\main.jar]

這個 main.jar 就是混淆后的jar包，只不過這個jar還包含了 R 類和 BuildConfig 類的信息，所以將這個信息過濾掉就可以。但問題也來了，jar包都已經打好了，怎么配置混淆？解決方法是只要把jar包當輸入就行了，最終配置如下：

task buildJar(type: Jar, dependsOn: ['assembleRelease']) {
    destinationDir = file('build/outputs/jar/')
    appendix = "" // SDK的后綴名稱
    baseName = "" // SDK名稱
    version = SDK_VERSION // 這個常量是在gradle.properties中配置的

    // manifest信息
    def map = ['Version': SDK_VERSION,
               'Gradle': project.gradle.gradleVersion,
               'Vendor': '',
               'Date': new Date().getDateTimeString()
        ]
    manifest.attributes(map)

    from(project.zipTree('build/intermediates/transforms/proguard/release/jars/3/3/main.jar'))
    exclude('**/BuildConfig.class')
    exclude('**/BuildConfig\$*.class')
    exclude('**/R.class')
    exclude('**/R\$*.class')
    include('**/*.class')
}

OK，任務搞定。

來自：http://www.jacpy.com/2017/02/28/android-studio-gradle-make-jar-and-proguard.html